It is known that the aqueous mixtures of two polymers such as poly(ethylene glycol) (PEG) and dextran can separate spontaneously into two aqueous phases, called aqueous two-phase systems. Phase separation in aqueous solutions of polymers is an extraordinary and underexplored phenomenon. When two aqueous solutions of polymers are mixed, the resulting system is not homogeneous; rather, two discrete phases, or layers, form. These layers are ordered according to density and arise from the limited interaction of the polymers for one another. In these systems, each phase predominantly consists of water (upwards of 70-90% (w/v)), while the polymer component is present in concentrations ranging from micromolar to millimolar. A low interfacial tension and rapid mass transfer of water-soluble molecules across the boundary characterize the interface between layers.
Previous studies of partitioning between aqueous phases have been limited to biphasic systems of immiscible polymers or inorganic salts. These Aqueous Two-Phase Systems (“ATPS”) are exemplified by the poly(ethylene glycol)-dextran, dextran-Ficoll systems, and a poly(ethylene glycol) system comprising (NH4)2SO4. Uses of these systems have focused on applications in protein chemistry, cell partitioning, and manufacturing.
Further, previous methods for separating and partitioning components have been limited to, e.g., filtration, crystallization, distillation, chromatography, and separation by hand. Many of these methods have been proven difficult, imprecise, slow, expensive, and unsuitable for use with diverse sample types and sizes, or otherwise undesirable.
There is a need for simple, precise methods for separating biological and non-biological samples based on density with multi-phase systems suitable for use with diverse sample types and sizes.